So basically I purchased this vehicle with 122,000 miles (now has 128,000) and notice the pressure gauge was maxed out (sending unit had gone bad), so I replaced it myself and everything was fine. About 2 weeks ago I changed the oil myself (pennzoil platinum, with a purolator filter). A few days later I was at a stop light and my oil pressure gauge needle caught my eye, it was bouncing up and down, but continued to inch down, but not to the point where it would set off anything on the instrument gauge. Light turned green, needle goes back to the half way point and stays consistent until next red light and same thing. Next day I paid attention more and noticed this only happens after driving for a period of time allowing the oil to heat up. I called my friend down at the local Nissan shop and said replace filter with OEM and start there. Changed it out 2 days ago and still the same. Anyone know anything about this issue or how to fix?? Thanks